Cosmic dust sensor

ABSTRACT

A sensor for detecting and measuring the energy, velocity and direction of travel of a cosmic dust particle, comprises an array of electrodes. Some of the electrodes are arranged in columns and spaced in close proximity to other electrodes that are disposed in rows. Together the columns and rows define a plurality of sectors through which a cosmic particle may traverse. Each electrode includes electrically biased conductor layers supported on an optically transparent matrix. Ions and electrons from an impacting cosmic dust particle compose an ionized plasma for collection on the electrically biased conductors, creating an electrical output pulse which may be amplified. A second array of electrodes in columns and grids in rows is included in spaced relationship from the first array. An impacting cosmic dust particle on the second array produces an electrical output pulse in the same manner as described. Should a particle penetrate the first array and impact upon the second spaced array, a pair of time spaced electrical outputs will result, the time spacing of the pulses being proportional to the velocity of the particle. The direction of the particle&#39;&#39;s travel, and thereby its origin in space is determined by the alignment of respective sectors traversed by the particle. Behind the second array is placed a microphone plate which arrests further penetration of the particle. The microphone output amplitude is an indication of the momentum of a particle. At least one of the secottors in each of the arrays is bounded by an epoxy coating rendering it impervious to plasma collection. Accordingly, a pulse output originated from the impervious sector gives an indication of noise or other interference collected by the sensor. Additionally, a second microphone of small area is segregated from the first-described microphone and is provided with a separate output. Accordingly, electrical signals from the small microphone which are disproportionate with respect to the small area of the second microphone are indicative of interfering noise as well as particle impact.

United States Patent [72] Inventor Otto E. Berg Forest Heights, Md. [2]Appl. No. 789,044 [22] Filed Dec. 31, 1968 [45] Patented Dec. 7, 1971The United States of America as represented by the Administrator of theNational Aeronautics and Space Administration [73] Assignee 54] COSMICDUST SENSOR 15 Claims, 4 Drawing Figs.

[52] U.S. Cl 250/83.6 R [51] Int. Cl G0 1/18 [50] Field of Search250/816,

Primary E.taminerJames W. Lawrence Assistant Examiner- Davis L. WillisAttorneys-R. F. Kempf, E. Levy and G. l. McCoy ABSTRACT: A sensor fordetecting and measuring the enery. velocity and direction of travel of acosmic dust particle, comprises an array of electrodes. Some of theelectrodes are arranged in columns and spaced in close proximity toother electrodes that are disposed in rows. Together the columns androws define a plurality of sectors through which a cosmic particle maytraverse Each electrode includes electrically biased conductor layerssupported on an optically transparent matrix. Ions and electrons from animpacting cosmic dust particle compose an ionized plasma for collectionon the electrically biased conductors. creating an electrical outputpulse which may be amplified. A second array of electrodes in columnsand grids in rows is included in spaced relationship from the firstarray. An impacting cosmic dust particle on the second array produces anelectrical output pulse in the same manner as described. Should aparticle penetrate the first array and impact upon the second spacedarray, a pair of time spaced electrical outputs will result, the timespacing of the pulses being proportional to the velocity of theparticle. The direction ofthe particles travel, and thereby its originin space is determined by the alignment of respective sectors traversedby the particle. Behind the second array is placed a microphone platewhich arrests further penetration of the particle. The microphone outputamplitude is an indication ofthe momentum ofa particle. At least one ofthe secottors in each of the arrays is bounded by an epoxy coatingrendering it impervious to plasma collection. Accordingly. a pulseoutput originated from the impervious sector gives an indication ofnoise or other interference collected by the sensor. Additionally, asecond microphone ofsmall area is segregated from the first-describedmicrophone and is provided with a separate output. Accordingly,electrical signals from the small microphone which are disproportionatewith respect to the small area of the second microphone are indicativeofinterfering noise as well as particle impact PATENTED DEC 7197:

SHEET 2 UF 2 QQ ND Qm mi wk wk VN mm NHL 8 INVENTOR 9 4 O'TTO E. BERG'7ATTORNEYS COSMIC DUST SENSOR The invention described herein was madeby an employee of the US. Government and may be manufactured or used byor for the US. Government for governmental purposes without the paymentof any royalties thereon or therefor.

The present invention relates generally to a particle sensor, and morespecifically, to a sensor for determining the density, velocity, kineticenergy and direction of particles, for example, cosmic dust particles. 7

The sensor according to the invention comprises a first and a secondarray of electrically biased, particle impact sensitive films. In eacharray, plurality of the films are arranged in sequential columns androws. The rows and columns define a plurality of adjacent sectors forregistering the location of a particle which imparts the array. Thefilms are fabricated from layers of a conductive material supported onan optically transparent matrix. The columns-and rows are electricallybiased positively and negatively, respectively. An impacting particleproduces an ionized plasma comprising ions and electrons, the positivelybiased columns collect the electrons and the negatively biased rowscollect the ions. Such collection produces an electrical output pulsefrom each of the columns and rows impacted by the particle, which pulsemay be detected, amplified and recorded. The amplitude of the pulse isindicative of particle energy. Additionally, each array may be boundedby outer enlarged, negatively biased films or grids which preventelectrons of the plasma produced at the array from escaping therefrom.

The two arrays, together with their boundary films are placed in spacedrelationship. An impacting particle which penetrates the first array andimpacts the second will thus produce electrical pulses in time spacedrelationship. The time spacing of the pulses is directly proportional toparticle velocity. The origin in space of the impacting particle isdetermined by the alignment of the sectors in each of the spaced arrayspenetrated by the particles.

Behind the second array is located a microphone plate which arrestsfurther penetration of an impacting particle. The output amplitude ofthe microphone upon impact by a particle is indicative of the particlesmomentum.

The number of array and microphone output pulses produced within apredetermined time period is indicative of particle density.

At least one sector of each array is provided with epoxy coveringsrendering such sectors impervious to collection of ionized plasma.Accordingly, pulse outputs from the impervious sectors are due to noiseor other interference. Similarly, a portion of the microphone sensor issegregated and provided with a separate output. Although the segregatedportion detects particle impact, ideally the electrical pulses resultingtherefrom should be proportionally reduced from those produced by themain portion of the microphone. Should such proportion of pulses vary,the disproportionate number of pulses thus produced is an indication ofnoise or other inter ference. Accordingly, the effect of the pulsesresulting from the impervious sectors and the segregated portion of themicrophone should be subtracted from the recorded pulse data in order togive a true indication of particle detection.

Accordingly, it is in object of the invention to provide a new andimproved particle sensor.

A further object of the invention is to provide a particle sensor whichmeasures the energy, momentum, velocity and direction of a particleimparting or penetrating the sensor.

Another object of the invention is to provide an acoustic sensor formeasuring the momentum of a particle impacting thereon.

Still another object of the invention is to provide a particle sensorhaving a noise and other interference detector adapted for the sameenvironment as the main sensor.

Other objects and many attendant advantages of the present inventionwill become apparent upon perusal of the following detailed descriptiontaken in conjunction with the accompanying drawings wherein:

FIG. 11 is a schematic representation of one of the films included ineach array of the present invention;

FIG. 2 is a schematic representation in perspective of a first arrayaccording to the invention that comprises a plurality of electricallybiased films arranged in sequential columns and rows;

FIG. 3 is a schematic representation in perspective of a second array offilms arranged in sequential columns and rows in combination with amicrophone detector; and

FIG. 4 is a diagrammatic representation illustrating the particledirection determining sectors provided by the spaced arrays.

With more particular reference to the drawings, there is shown generallyat in FIG. 1 an exploded view in schematic of a particle detecting filmaccording to the invention. More specifically, the film comprises a3,000A.-thick substrate layer 12 of Parylene, a commercially availableproduct of Union Carbide Corporation, Greenville, SC. The surfaces ofthe Parylene substrate layer are provided with opposed aluminum layers14 and 16 of aluminum, which layers are 300A. in thickness and applied,for example, by film evaporation bath techniques. The aluminum surfacedParylene substrate layer 112 is provided with opposed copper layers 18and 20 which are 500A. thick and respectively applied directly over thealuminum layers 14 and 16, by film evaporation bath techniques. Aluminumlayers 14 and 16 are provided to protect the Parylene substrate layer I2from damage while the copper layers l8 and 20 are applied thereon.

The copper layer 118 may be provided thereover with an overlying supportmesh 22, preferably comprising a commer cially available opticallytransparent nickel mesh manufactured by the Buckbye-Meers Corporation,Minneapolis, Minn. The grid 22 is made to adhere to the copper layer ll8by interposing therebetween a thin film of a dielectric bonding agent,such as a commercially available liquid polysiloxane. A SODA-thickencapsulation layer 24 overlies the support mesh 22. The remainingcopper layer 20 is provided with an overlying 700A.-thick layer 26 ofParylene.

Accordingly, the structure thus described provides a multilayercomposite film, the support mesh 22 providing mechanical rigidity to thefilm and the encapsulation layers 24 and 26 serving to isolate thecopper layers 18 and 20 from the corrosive effect of ambient atmosphere.

With reference to FIG. 2, there is shown generally a first array 28 offilms 10 arranged in spaced sequential columns and rows. Array 28 isillustrated schematically and in perspective as including a firstelectrode 30 that includes four composite, metal films l0, insulatedfrom each other in rectangular strip form and arranged in parallelspaced relationship to form a coplanar row of composite films.Similarly, four additional composite metal strips or 10 films insulatedfrom each other of similar rectangular strip configuration are disposedin parallel spaced relationship to form coplanar columns of stripscomprising electrode 32. Electrode 34lincludes, four additionalcomposite, strips 10 insulated from each other of rectangular stripconfiguration that are placed in adjacent spaced relationship to formcoplanar row of composite strips. Accordingly, the rows and columns ofthe strips comprising electrodes 30, 32 and 34 together comprise spacedsequential alternate rows and columns of particle detecting films.

The array 28 is further provided with outer boundaries defined bycomposite metal films that form electrodes 36 and 38. Each of the films36 and 38 is similar in fabrication to the composite film 10 of FIG. I.The boundary films 36 and 39 and the rows and columns 30, 32 and 34 areretained in adjacent parallel relationship by any well-known mechanicalsupporting means (not shown). Additionally, the boundary films 36 and 38and the rows and columns 30, 32 and 341 are of the same area.

The boundary films 36 and 38 are provided with electrical conductors,illustrated schematically at 40 and 42. Both conductors 40 and 42 areconnected at 44 to a source of electrical potential (not shown) whichbiases the copper layers in each of the composite films 36 and 38 to aminus 7v.-potential. Each of the adjacent composite films 10 in the rows30 and 34 is provided with an electrical conductor. More specifically,each of four conductors 46, 48, 50, and 52, is respectively connected toa corresponding pair of composite film strips 10, the strips of eachpair being selected from both electrode rows 30 and 34. Accordingly, thecorresponding horizontally elongated composite strips of electrode rows30 and 34 are provided with a common conductor. The conductors 46, 48,50 and 52 are respectively connected to amplifiers illustratedschematically at 54, 56, 58 and 60. Additionally, each of the conductorsis connected as shown generally at 62 to a source of electricalpotential (not shown) which biases the corresponding film strip in therows 30 and 34 to a positive 24v.- potential.

In similar fashion, each vertically extending composite strip 10 of thecolumn electrode 32 is provided with separate conductors 64, 66, 68and'70 as schematically illustrated in FIG. 2. Each of the conductors isconnected with a separate one of amplifiers 72, 74, 76 and 78.Additionally, each of the conductors 64, 66, 68 and 70 is connectedthrough resistors 80 to a source of electrical potential (not shown)which electrically biases each of the column electrodes 32 to a minus3.5 potential.

With reference to FIG. 4, taken in conjunction with FIG. 2, the row andcolumn electrodes 30, 32 and 34 provide, as shown schematically in FIG.4, a plurality of adjacent sectors, 16 in number. More specifically,each sector is defined by an area formed by the overlapped portion ofeach of the column composite strips with the adjacent rows of strips ineach of the rows 30 and 34. Since there are four strips arranged inrectangular columns and four strips arranged in each of the rectangularrows, 16 rectangular sectors are provided. For example, with referenceto FIG. 2 one of such sectors is illustrated generally in dotted outlineat 82. In FIG. 4, the end of the rectangular sector 82 is illustratedwith grid shading. The superimposed portions of the composite filmstrips disposed within the sector 82 are provided with a coating ofepoxy similar in configuration to the grid shaded end portion of thesector 82. For example, as shown in exploded form in FIG. 2, theportions of the boundary films 36 and 38 are disposed within the sector82 are covered with epoxy layers 84 and 86 respectively. Similarly, theportions of the composite films in each of the rows 30 and 34 disposedwithin the sector 82 are covered with epoxy layers 88 and 90,respectively. The por tion of the columns of films 32 disposed withinthe sector 82 is covered with a layer of epoxy 92.

With reference to FIG. 3, there is shown generally a second array 94 ofparticle detecting films similar in configuration to the first array 28of FIG. 2 A plurality of a particle detecting films 10 as described withreference to FIG. 1, are of generally rectangular strip configurationand disposed in adjacent parallel coplanar relationship to form a row offilm electrodes 96. Four additional strip configured particle detectionfilms 10 are arranged in adjacent parallel relationship to form coplanarcolumns of detection electrodes 98.

Disposed in parallel adjacent spaced relationship from the row 96 ofdetector films is an enlarged boundary film 100 similar in fabricationto the particle detection strip 10 as described in FIG. 1. An enlargedmicrophone plate 102 is disposed in parallel spaced relationship withrespect to the columns 98 of particle detection films. The microphoneplate 102 is a one-sixteenth inch thick quartz acoustical sensor platehaving a 60 micron thick molybdenum layer cemented thereon, themolybdenum layer facing the columns 98 of particle detecting film.

The microphone plate 102 is provided with a generally central well-knownmicrophone button 104. A portion 106 of the microphone plate 102 issegregated from the main portion 104. The segregated portion 106 isone-fifteenth of the total area of the remaining portion of themicrophone plate 102 and is provided with a separate well-knownmicrophone button 108. The enlarged boundary film 100 and the microphoneplate 102, together with its segregated portion 106, are of the samearea and are maintained in adjacent spaced relationship by anywell-known mechanical support means (not shown).

The row and column electrodes 96 and 98 of particle detecting filmsappear superimposed, as shown in FIG. 4, to form a plurality of adjacentsectors. More specifically, with reference to FIG. 4, taken inconjunction with FIG. 3, one of the sectors is illustrated schematicallyin dotted outline by rectangular sector 110. With reference to FIG. 4,the end portion of the exemplary sector 110 is illustrated in gridshading. Additionally, the microphone plate output 104 is illustratedschematically generally centrally of the sectors in the array 94. Thesegregated portion 106 of the microphone plate is illustrated as itwould appear in its relationship with the sectors formed by thesuperimposed rows and columns of strip detector films.

With reference to FIG. 3, each superimposed portion of the films in thearray 94 which are within the exemplary sector is covered with an epoxycoating. For example, the portion of the boundary film 100 within thesector 110 is provided with a coating 112 of epoxy, illustrated inexploded configuration. Similarly, the portion of the rows 96 of theparticle detection films 10 which is within the sector 110 is providedwith an epoxy coating 114. The portion of the columns 96 of particledetection films within the sector 110 is covered with a coating ofepoxy, shown in exploded form at 116.

The boundary film 100 is provided with an electrical conductor 118 whichis connected to a source of electrical potential (not shown) whichbiases the conductive copper layers within the film 100 to a minus 7volts potential. The strip films in row electrodes 96 of particledetecting films are respectively connected to conductors 120, 122, I24and 126. Each of the conductors is connected through resistors 128 to asource of electrical potential (not shown) which biases each of theconductive copper layers within the row electrode 96 of particledetecting films to a plus 24 volts potential. Additionally, each of theconductors 120, 122, 124 and 126 connects a respective film to the inputof a different one of amplifiers 130, 132, 134 and 136. Each of thecolumns 98 of particle detecting film is corrected to a different one ofconductors 138, 140, 142 and 144. The conductors are connected throughresistors 146 to a source of electrical potential (not shown) whichbiases each of the conductive copper layers within the columns 98 offilm detectors to a minus 3.5 volts potential. Further, each of theconductors 138, 140, 142 and 144 con nects a respective strip filmdetector to the input of a different one of amplifiers 148, 150, 152 and154.

With reference to Fig. 4, the first and second arrays 28 and 94 aresupported in parallel relationship, spaced from each other by adistance, shown generally at 156, of 10 centimeters. Each rectangularsector in the array 28 has an exemplary cross section of l square inch.A one-eighth inch spacing is maintained between each of the parallelsuperimposed layers of strips included in electrodes 36, 30, 32, 34 and38, thereby lending a depth of approximately one-half inch to each ofthe sectors in the array 28.

With reference to FIG. 3, it is seen that a one-eighth inch spacing ismaintained between each of the boundary film 100, the rows of films 96,the columns of films 98 and the microphone plate 102, whereby the depthof each of the sectors, for example the sector 112 is approximatelythreeeighths of an inch.

In operation, a cosmic dust particle to be detected impacts andpenetrates the first array 28. Upon impact with the array an ionizedplasma is generated by the film 32. The ions and electrons of the plasmaare collected on the electrically biased copper layers of the rows andcolumns of strips in electrodes 30, 32 and 34. More specifically, thepositive ions of the plasma returns to and are collected on thenegatively biased columns of electrode 32 of particle detecting strips10 thereby producing an electrical pulse output at the output of atleast one of the amplifiers 72, 74, 76 or 78. The electrons of theplasma are collected on both of the row electrodes 30 and 34 of particledetecting strips thereby producing an electrical output pulse at theoutput of at least one of the amplifiers S ll, 56, 58 and 60. Theboundary films or electrodes 36 and are negatively biased to preventescape of the generated electrons from the array 20. Positive ions inthe plasma generated by electrodes 32 are repelled by the negative biasof the strips in electrodes 30 and 34. The energy of the impactingcosmic dust particle is directly proportional to the amplitude of theelectrical pulses produced by the amplifiers. Additionally, the sectorin which the impacting particle has traversed is indicated by whichcombination of the amplifiers produces the electrical output resultingfrom ionized plasma generation by the im' pacting particles. If animpacting particle is of insufficient energy to penetrate the array 28,the amplitude of the resulting output pulse is also a measure of thekinetic energy of the impacting particle.

[f a particle is of sufficient energy to penetrate the array 20 andimpact the array 94, an ionized plasma is produced from impact with saidarray 90. Positive ions are collected on the columns of electrode 08 ofparticle detecting films, whereby an output pulse is delivered from oneof the amplifiers i140, 1150, 1152 or 154i. Additionally, the electronsof the produced ionized plasma are collected on the rows of electrode96, thereby producing an electrical output pulse at the output of atleast one of the amplifiers 1130, 132, 134 and 1136. The boundary film100 is negatively biased to repel electrons of the ionized plasma andthereby prevent escape thereof from the array 9 0. By determining whichcombination of amplifiers produces the output upon impact of a particle,it can be deter mined in which sector the particle impacts the array94$. Accordingly, by aligning the respective impacted sectors in each ofthe arrays 28 and 94, the velocity vector and thereby the direction ofthe origin in space of the impacting cosmic dust particle may bedetermined.

The pulse outputs from the array 20 is in time spaced relationship withrespect to the pulse outputs from the array 94. The time spacing betweenthe outputs of arrays 20 and 94- is inversely proportional to thevelocity of the impacting cosmic dust particle.

Upon impact with the array 94, the cosmic dust particle is stopped fromfurther penetration by impact upon the microphone plate 102.Accordingly, the particle transfers all its remaining energy to themicrophone plate 102 and produces an acoustic output as a resultthereof. The amplitude of the microphone output is thus directlyproportional to the momentum of the impacting particle.

A distinguishing feature of the present invention is that the sector 02,containing the epoxy coatings $4, 86, 00, 90 and 92 is impervious toionized plasma collection, thereby obviating a simultaneous output overthe combination of amplifiers 54 and 70. Should such simultaneousoutputs occur, they are not due to cosmic dust impact but to electricalnoise or other electrical interference. The frequency of suchsimultaneous pulse output may be compared with the frequency of outputsof the entire array 20 in order to determine the accuracy of the outputpulses of the amplifiers as representative of the number of actualimpacts by cosmic dust particles.

In similar fashion, the sector 110 of the array 94 is provided with thedielectric coatings 1112, 114 and 1 16 which are impervious to thecollection of ions or electrons produced by an impacting particle.Hence, any output signals simultaneously derived from each of amplifiers136 and M0 is due to electrical noise or other interference.

The segregated portion 1106 of the microphone plate 102 is approximatelyone-fifteenth the area of the remaining portion of the microphone plate.Accordingly, during operation electrical pulses produced at the outputs104 and 100 should have an amplitude ratio of 15 to 1. If a greaterratio of pulses is produced by the outputs 1104- and 108, the pulses aredue to electrical noise or other electrical interference. Accordingly,the proper ratio of output pulses is indicative of the reliability ofthe output pulses as a measure of particle momentum.

Another feature of the apparatus is that the physical and electronicconditions thereof may be checked. The films of each array are closelyspaced and have therebetween an appreciable relative capacitance.Accordingly, a large electrical pulse may be generated by a suitablecommand signal and impressed on each of the arrays to induce viacapacitance an electrical pulse output over the associated amplifiers.The presence of electrical pulses over the amplifiers in response to theimpressed electrical pulse is indicative that the arrays are operative.Accordingly, the proper performance of array may be easily checked bythe prescribed procedure.

In actual practice the boundary films 36, 30 and 1100 may alternativelycomprise open mesh grids, to enable cosmic dust particles to passthrough them more readily. Accordingly, either films or grids may beutilized in preferred embodiments of the invention.

Similarly, in each of the arrays 28 and 94, the rows 30, 3s and 96 offilms may alternatively comprise open mesh grids in preferredembodiments of the invention to enable the dust particles to passthrough them.

Other modifications and embodiments of the present invention may befabricated without departures from the scope of the invention asdescribed in the appended claims.

What is claimed is:

l. A detector for cosmic dust or other similar outer space particlescomprising biased first electrode means for deriving a plasma stream inresponse to said particles impinging thereon, second electrode meansbiased with the opposite polarity from said first electrode means forcollecting charged carriers in the plasma stream, means connected tosaid first electrode means for deriving a first signal in response tothe plasma stream being derived by the first electrode means and chargedcarriers in the stream returning to the first electrode means, and meansconnected to said second electrode means for deriving a second signal inresponse to charged carriers from the plasma stream being collectedthereby, said first electrode means including a first plurality ofstrips insulated from each other and having parallel longitudinal axesextending in a first direction, said second electrode means including asecond plurality of strips insulated from each other and having parallellongitudinal axes extending in a second direction at right angles to thefirst direction, and means responsive to said first and second signalsfor indicating the strips of the first and second plurality whichreceive the charged carriers.

2. The detector of claim 1 further including a third electrode meanspositioned in the path of charged carriers in the stream that passthrough the second electrode means, said third electrode means beingbiased to repel the charged carriers passing through the secondelectrode means.

3. The detector of claim 1 wherein said second electrode means includesfirst and second elements respectively positioned proximate oppositefaces of said first electrode means, said first element being configuredto enable the particles to pass through it so that they can impinge onthe first electrode means.

4-. The detector of claim ll wherein the first element is a mesh.

5. A detector for cosmic dust or other similar outer space particlescomprising first biased electrode means for deriving a plasma stream inresponse to said particles impinging thereon, second electrode meansbiased with the opposite polarity from said first electrode means forcollecting charged carriers in the plasma stream, at least one of saidelectrodes being segmented into areas insulated from each other, each ofsaid areas defining an impact area for charged carriers in the plasmastream, and means connected to said areas for deriving an indication ofthe area onto which the charged carriers impact.

6. A detector for cosmic dust or other similar outer space particlescomprising first biased electrode means for deriving a plasma stream inresponse to said particles impinging thereon, second electrode meansbiased with the opposite polarity from said first electrode means forcollecting charged carriers in the plasma stream, a third electrodemeans positioned in the path of charged carriers in the stream that passthrough the second electrode means, said third electrode means beingbiased to repel the charged carriers passing through the secondelectrode means.

7. A detector for cosmic dust or other similar outer space particlescomprising first biased electrode means for deriving a plasma stream inresponse to said particles impinging thereon, second electrode meansbiased with the opposite polarity from said first electrode means forcollecting charged carriers in the plasma stream, means connected to oneof said electrode means for deriving a signal in response to chargedcarriers from the plasma stream being collected thereby, said secondelectrode means including first and second elements respectivelypositioned proximate opposite faces of said first electrode means, saidfirst element being configured to enable the particles to pass throughit so that they can impinge on the first electrode means.

8. The detector of claim 7 wherein the first element is a mesh.

9. The detector of claim 7 wherein the first element is a thin film.

10. The detector of claim 7 further including a third electrode meanspositioned in the path of charged carriers in the stream that passthrough the second electrode means, said third electrode means beingbiased to repel the charged carriers passing through the secondelectrode means.

11. The detector of claim 10 wherein the third electrode means includesthird and fourth elements respectively positioned outside the first andsecond elements of said second electrode, said first and third elementsbeing configured to enable the particles to pass through them so thatthe particles can impinge on the first electrode means.

12. The detector of claim 7 wherein said first electrode means includesa first plurality of strips insulated from each other and havingparallel longitudinal axes extending in a first direction, said secondelectrode means includes a second plurality of strips insulated fromeach other and having parallel longitudinal axes extending in a seconddirection at right angles to the first direction, and means responsiveto said first and second electrode means collecting charged carriersfrom the stream for indicating the strips of the first and secondplurality which receive the charged carriers.

13. A detector for enabling the velocity vector of cosmic dust or othersimilar outer space particles to be determined comprising a first arrayincluding:

first biased electrode means for deriving a first plasma stream inresponse to said particles impinging thereon, second electrode meansbiased with the opposite polarity from said first electrode means forcollecting charged carriers in the first plasma stream, both of saidfirst and second electrodes being segmented into areas insulated fromeach other, each of said areas defining an impact area for chargedcarriers in the first plasma stream, and means connected to said areasdefined by the first and second electrodes for deriving an indication ofthe area of the first array onto which the charged carriers of the firststream impact; a second array positioned downstream of the first array,said second array including: third biased electrode means for deriving asecond plasma stream in response to said particles impinging thereon,fourth electrode means biased with the opposite polarity from said thirdelectrode means for collecting charged carriers in the second plasmastream, both of said third and fourth electrodes being segmented intoareas insulated from each other, each of said areas defining an impactarea for charged carriers in the second plasma stream, and meansconnected to said areas defined by the third and fourth electrodes forderiving an indication of the area of the second array onto which thecharged carriers of the second stream impact.

14. The detector of claim 13 further including means responsive to thesignals for enabling an indication of the velocity of the particles tobe derived.

15. A particle impact sensor apparatus comprising:

first array of electrically conducting films, second array ofelectrically conducting films in spaced relationship with respect tosaid first array, first electrical output means associated with saidfirst array, second electrical output means associated with secondarray, time spaced electrical signals being produced by said first andsecond output means in response to a particle impacting said arrays,each of said arrays being electrically biased to collect ionized plasmaproducts resulting from impacting by said particle, each of said arrayshaving electrically positive biased films and electrically negativebiased films, said positively biased films being arranged in coplanarrows, said negative biased films being arranged in coplanar columns,said columns and rows being superimposed, a plurality of sectors eachdefined by a corresponding pair of superimposed column and row arrangedfilms, said electrical output means producing the electrical signals insuch a manner as to identify the particular sectors impacted by theparticle, portions of the films within at least one of said sectors ineach array being provided with dielectric coatings impervious toparticle impact thereon.

1. A detector for cosmic dust or other similar outer space particlescomprising biased first electrode means for deriving a plasma stream inresponse to said particles impinging thereon, second electrode meansbiased with the opposite polarity from said first electrode means forcollecting charged carriers in the plasma stream, means connected tosaid first electrode means for deriving a first signal in response tothe plasma stream being derived by the first electrode means and chargedcarriers in the stream returning to the first electrode means, and meansconnected to said second electrode means for deriving a second signal inresponse to charged carriers from the plasma stream being collectedthereby, said first electrode means including a first plurality ofstrips insulated from each other and having parallel longitudinal axesextending in a first direction, said second electrode means including asecond plurality of strips insulated from each other and having parallellongitudinal axes extending in a second direction at right angles to thefirst direction, and means responsive to said first and second signalsfor indicating the strips of the first and second plurality whichreceive the charged carriers.
 2. The detector of claim 1 furtherincluding a third electrode means positioned in the path of chargedcarriers in the stream that pass through the second electrode means,said third electrode means being biased to repel the charged carrierspassing through the second electrode means.
 3. The detector of claim 1wherein said second electrode means includes first and second elementsrespectively positioned proximate opposite faces of said first electrodemeans, said first element being configured to enable the particles topass through it so that they can impinge on the first electrode means.4. The detector of claim 1 wherein the first element is a mesh.
 5. Adetector for cosmic dust or other similar outer space particlescomprising first biased electrode means for deriving a plasma stream inresponse to said particles impinging thereon, second electrode meansbiased with the opposite polarity from said first electrode means forcollecting charged carriers in the plasma stream, at least one of saidelectrodes being segmented into areas insulated from each other, each ofsaid areas defining an impact area for charged carriers in the plasmastream, and means connected to said areas for deriving an indication ofthe area onto which the charged carriers impact.
 6. A detector forcosmic dust or other similar outer space particles comprising firstbiased electrode means for deriving a plasma stream in response to saidparticles impinging thereon, second electrode means biased with Theopposite polarity from said first electrode means for collecting chargedcarriers in the plasma stream, a third electrode means positioned in thepath of charged carriers in the stream that pass through the secondelectrode means, said third electrode means being biased to repel thecharged carriers passing through the second electrode means.
 7. Adetector for cosmic dust or other similar outer space particlescomprising first biased electrode means for deriving a plasma stream inresponse to said particles impinging thereon, second electrode meansbiased with the opposite polarity from said first electrode means forcollecting charged carriers in the plasma stream, means connected to oneof said electrode means for deriving a signal in response to chargedcarriers from the plasma stream being collected thereby, said secondelectrode means including first and second elements respectivelypositioned proximate opposite faces of said first electrode means, saidfirst element being configured to enable the particles to pass throughit so that they can impinge on the first electrode means.
 8. Thedetector of claim 7 wherein the first element is a mesh.
 9. The detectorof claim 7 wherein the first element is a thin film.
 10. The detector ofclaim 7 further including a third electrode means positioned in the pathof charged carriers in the stream that pass through the second electrodemeans, said third electrode means being biased to repel the chargedcarriers passing through the second electrode means.
 11. The detector ofclaim 10 wherein the third electrode means includes third and fourthelements respectively positioned outside the first and second elementsof said second electrode, said first and third elements being configuredto enable the particles to pass through them so that the particles canimpinge on the first electrode means.
 12. The detector of claim 7wherein said first electrode means includes a first plurality of stripsinsulated from each other and having parallel longitudinal axesextending in a first direction, said second electrode means includes asecond plurality of strips insulated from each other and having parallellongitudinal axes extending in a second direction at right angles to thefirst direction, and means responsive to said first and second electrodemeans collecting charged carriers from the stream for indicating thestrips of the first and second plurality which receive the chargedcarriers.
 13. A detector for enabling the velocity vector of cosmic dustor other similar outer space particles to be determined comprising afirst array including: first biased electrode means for deriving a firstplasma stream in response to said particles impinging thereon, secondelectrode means biased with the opposite polarity from said firstelectrode means for collecting charged carriers in the first plasmastream, both of said first and second electrodes being segmented intoareas insulated from each other, each of said areas defining an impactarea for charged carriers in the first plasma stream, and meansconnected to said areas defined by the first and second electrodes forderiving an indication of the area of the first array onto which thecharged carriers of the first stream impact; a second array positioneddownstream of the first array, said second array including: third biasedelectrode means for deriving a second plasma stream in response to saidparticles impinging thereon, fourth electrode means biased with theopposite polarity from said third electrode means for collecting chargedcarriers in the second plasma stream, both of said third and fourthelectrodes being segmented into areas insulated from each other, each ofsaid areas defining an impact area for charged carriers in the secondplasma stream, and means connected to said areas defined by the thirdand fourth electrodes for deriving an indication of the area of thesecond array onto which the charged carriers of the second streamimpact.
 14. ThE detector of claim 13 further including means responsiveto the signals for enabling an indication of the velocity of theparticles to be derived.
 15. A particle impact sensor apparatuscomprising: first array of electrically conducting films, second arrayof electrically conducting films in spaced relationship with respect tosaid first array, first electrical output means associated with saidfirst array, second electrical output means associated with secondarray, time spaced electrical signals being produced by said first andsecond output means in response to a particle impacting said arrays,each of said arrays being electrically biased to collect ionized plasmaproducts resulting from impacting by said particle, each of said arrayshaving electrically positive biased films and electrically negativebiased films, said positively biased films being arranged in coplanarrows, said negative biased films being arranged in coplanar columns,said columns and rows being superimposed, a plurality of sectors eachdefined by a corresponding pair of superimposed column and row arrangedfilms, said electrical output means producing the electrical signals insuch a manner as to identify the particular sectors impacted by theparticle, portions of the films within at least one of said sectors ineach array being provided with dielectric coatings impervious toparticle impact thereon.